Nearly all polymeric materials undergo oxidation reactions with oxygen. These reactions can occur with or without the assistance of ultraviolet light. In polyurethane foams, it is known that the foam suffers from the problem of discoloration arising from oxidation reactions and NOx fumes commonly formed in warehouses heated by natural gas combustion, as well as discoloration due to normal light exposure. It is also known that aromatic amine scorch inhibitors used in polyurethane foam formulations further add to polyurethane discoloration and in fact significantly advance color onset. To date, strategies used to reduce discoloration have involved scorch inhibitor reformulation such as using low or no aromatic amine blends. Otherwise, polyurethane foam fabricators have few tools at their disposal, apart from mechanical shielding of foam, to prevent the color fade phenomenon.
Polyurethane foams are known to photo oxidize at wavelengths primarily below 320 nm, but degradation of foams has been observed at wavelengths as high as 410 nm.
It has now been discovered that a combination of liquid organic UV inhibitors and antioxidants, in an aqueous or organic solvent base, provides an effective composition for reducing discoloration caused by the oxidation and photooxidation of the foam.